Contour Patterns & Cross Sections

Contour lines are one of the most powerful tools on a map. They allow you to visualise the three-dimensional shape of the land on a two-dimensional surface. At GCSE you need to be able to interpret contour patterns to identify landforms and draw accurate cross sections. This lesson covers both skills in detail.

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What Are Contour Lines?

A contour line joins all the points that are at the same height above sea level. On OS maps:

• Contour lines are drawn in brown (or orange)
• The contour interval is usually 10 metres (i.e. each line represents a 10 m height difference)
• Every fifth contour line is drawn thicker and labelled with its height — these are called index contours (e.g. 50, 100, 150, 200)
• The numbers on contour lines always read so that uphill is at the top of the number

Exam Tip: If you cannot see a height label on a contour line, count up or down from the nearest index contour in steps of 10 m.

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Reading Contour Patterns

The spacing of contour lines tells you about the steepness of the land: